Electrical transformer windings



Dec. 17, 1957 s. HORELICK 2,817,065

ELECTRICAL TRANSFORMER WINDINGS Original Filed July 23, 1947 2Sheets-Sheet 1 Lek/for W 1 \S/JMUEL f/OREL/C/f Dec. 17, 1957 s. HORELICK2,817,065

ELECTRICAL TRANSFORMER WINDINGS Original Filed July 23, 1947 2Sheets-Sheet 2 INVENTOR 6901051. Hams; I /f United States Patent Ofiice2,817,065 Patented Dec. 17, 1957 ELECTRICAL TRAN SFORNIER WINDINGSSamuel Horelick, Pittsburgh, Pa., assignor, by mesne assignments, toMcGraw Electric Company, a corporation of Delaware Original applicationJuly 23, 1947, Serial No. 763,082. Divided and this application March16, 1953, Serial No. 348,179

9 Claims. 01. 336-58) This invention relates to electrical transformerWinding-s and, in particular, to high-voltage windings for powertransformers and the manufacture thereof.

The high-voltage windings of power transformers are usually of eitherthe pancake or helical type. Immersion of such windings in oil or otherinsulating liquid is usually the best method of insulating against thehigh voltages for which power transformers are designed. High-voltagewindings of the type mentioned, however, as constructed heretofore, havelacked the mechanical strength to resist distortion caused byelectromagnetic forces resulting from short-circuit, despite the factthat they are usually clamped under pressure between end plates. Toimpart the necessary strength and rigidity to the windings, it has beencustomary to dip them in varnish. This treatment, however, is not freefrom objections. The varnish being oil-proof prevents the insulating oilfrom penetrating through the insulation surrounding each turn of wire.There is also the danger of trapping air in the turn insulation so thatit cannot be removed but remains as a weak point in the insulation and apossible cause of breakdown of the insulation.

I have invented a novel transformer winding which overcomes theaforementioned objections. The present application is a division of mycopending application, Serial No. 763,082, filed July 23, 1947, now U.S. Patent No. 2,654,142, covering the method of constructing my noveltransformer winding. My improved winding has the turns of each coilbonded together and adjacent coils bonded to each other by radialspacers coated with a heatreactive compound such as shellac, to form anintegral mass strong enough to resist short-circuit stresses without thenecessity of dipping in varnish. In making the improved winding, if itis of the pancake type, I assemble the coils with shellac-coated spacerstherebetween. In the case of a helical winding, I insert the spacersbetween turns. I then apply pressure axially of the completed windingand subject it to heat while maintaining pressure thereon, thus curingor polymerizing the shellac after an initial softening thereof, andpermanently staying the several coils of a pancake winding or the coilturns of a helical winding by bonding them firmly to the spacers. Theresulting adhesion gives the winding the mechanical strength necessaryto withstand short circuits safely and, at the same time, leaves theturns largely exposed to the oil for easy penetration thereby of theturn insulation, free of the oil-proofing effect of the varnish coatingwhich has been applied previously.

A complete understanding of the invention may be obtainedfrom thefollowing detailed description and explanation which refer to theaccompanying drawings illustrating the present preferred embodiment andpractice. In the drawings,

Figure 1 is an elevation partly in section showing a winding assembledfrom a plurality of pancake coils and spacers, compressed between endplates;

Figure 2 is a partial plan view thereof partly broken away;

Figure 3 is a partial horizontal section to enlarged scale showing theconnection between the radial spacers and vertical spacer-s; and

Figure 4 is a partial elevation similar to Figure 1 showing theinvention applied to a helical winding.

Referring in detail to the drawings and, for the present, to Figures 1through 3, a high-voltage transformer winding of the pancake typeindicated generally at 10 is built up on a composite cylindricalinsulation barrier 11 having flanges and end rings 12. In the completedtransformer the low-voltage windings (not shown) are disposed within thebarrier 11 and one leg of the laminated core extends through them. Thebarrier 11 is composed of alternating, laminated tubes 13 and spacerstrips 14 spaced circumferentially thereof. The tubes are preferably oflaminated paper and the spacer strips of pressboard. The flanges or endrings 12 are composed of washers 15 and radial spacers 16 and 16a spacedcircumferentially thereof. Angle collars 17 have horizontal flangesdisposed between the washers and cylindrical necks 18 fitting down intothe tubes 13. The washers 15, spacers 16 and 16a and angle collars 17are of pressboard. Static shield rings 19 are disposed between theflanges 12 and the winding 10.

The complete high-voltage winding 10 is assembled in the known mannerfrom pancake coils 20, washers 15 and collars 17, spacers 16 and 16a,tubes 13 and spacer strips 14. Vertical spacer strips 14a are placed incircumferentially spaced relation about the outermost tube 13a. Thesespacer strips are of dovetail shape as shown in Figure 3 and are appliedto the tube 13a with their narrower side innermost. They mayconveniently be secured to the tube temporarily by any convenient means.

Pressboard washers 21 are disposed between the pancake coils 20 of eachpair. Similar washers 21a are disposed between the top and bottom coilsand the static shield rings. Between each successive pair of coils 20 Iinsert radial spacers 22 of pressboard, in circumferentially spacedrelation as shown in Figure 2. The spacers 22 are notched at their innerend as indicated at 23 for anchorage to the vertical spacer strips 14a.

The washers 21 and the spacers 22 have their to and bottom surfacescoated with a layer of heat-reactive material such as shellac or othermaterial which softens and becomes tacky when first heated and is thenpolymerized or cured and converted permanently so that it retains thesolid state even on subsequent heating. Numerous synthetic resins havethis property as well as natural shellac. These compounds are preferablyapplied to the washers and spacers by dissolving them in a volatilesolvent and brushing or spraying the solution on the surfaces of theseparts. After drying, the parts have a thin film of solid shellac orother compound on the surfaces thereof which are engaged by the turns ofthe coils 20 when the winding it) is assembled.

When the winding 1% has been completely assembled on the barrier 11 withthe flanges 12, I clamp the entire assembly between end plates 24 and25. The end plates may be drawn together by through bolts 26.Compression springs 27 are disposed under the nuts at one end of thebolts and the nuts are turned down sufliciently to compress the springsso that if the winding shrinks during subsequent processing to bedescribed shortly, the springs will expand and continuously maintain acertain degree of pressure on the Winding.

When the winding has been clamped between the end plates, I subject itto heating for several hours at a moderate temperature suflicient todrive off any moisture and to polymerize or cure the film or layer ofshellac or other similar material on the surfaces of the washers 21 andspacers 22 in contact with the top and bottom faces of the coils 20. Asthe winding is heated to the curing temperature of the shellac coatingon the washers and spacers, the shellac first softens and becomes tacky.As polymerization proceeds, the material cures or sets permanently inthe form of a solid which thereafter remains substantially rigid. Bymaintaining the coils in contact with the washers and spacers underpressure throughout the heating period, I thus obtain a firm bondbetween them as the shellac is cured after which the washers and spacersserve to stay the turns of the coils. In fact, the entire winding Mlbecomes a more or less integral mass after being heated. The radialspaces between the spacers 22 provide passages for insulating oil tofiow radially through the winding and afford free access thereof tosubstantially all portions of the coils 20 when the completed winding isassembled with the low-voltage windings and core and immersed in theusual tank filled with oil. The oil thus readily penetrates the paperwrapping on the turns of the coils 2t) and fills all the spaces betweenturns and between adjacent coils, eliminating any air pockets whichwould constitute a weak point in the transformer insulation.

As previously pointed out, the springs 27 cause the end plates 2 and 25to continue to apply pressure to the winding even after the shrinkagethereof incident to drying. After the winding has been heated for aperiod sufficient to dry it thoroughly and cure the shellac coating onthe washers and spacers, the end plates are removed and the high-voltagewinding is then ready for assembly with the low-voltage windings andcore. The windings are secured to the core in the usual manner and theusual clamping bars applied across the ends of the windings andconnected together by tie rods in the customary way.

Figure 4 shows a winding 2&3 similar to that shown at except that,instead of being composed of stacked pancake coils 20, it is formed bywinding a plurality of conductors disposed side-by-side in a continuoushelix. The turns of the helix are maintained in spaced relation byspacers 22a similar to the spacers Z2 and strung on spacer strips 14a inthe same manner as the latter. The winding 28 does not include anywashers El since the turns are helical instead of being of fiat, pancakeshape. The spacers 22a are coated with shellac or similar compound inthe manner already explained and the winding 28 is processed in the sameway as the winding 10.

It will be apparent from the foregoing that the invention provides atransformer winding having important advantages over the high-voltagetransformer windings made by the method known previously. In the firstplace, a winding according to my invention is insulated by the maximumdielectric value of the medium employed, i. e., oil, since air pocketsare avoided and free access for the. oil is afforded to all portions ofthe winding. Secondly, the bonding of the winding turns to the radicalspacers and washers, if used, serves to stay the turns and maintain themrigidly in proper relative position under the stress resulting fromshort-circuit, thus avoiding distortion and possible breakdown. Inaddition, the cost of the varnish treatment used heretofore, which issubstantial, is avoided. The cost of coating the washers and spacerswith shellac or similar compound is materially less than the cost of thevarnish treatment.

Although I have illustrated and described but a preferred embodiment andpractice with a modification, it will be recognized that changes in thedetails of the procedure and construction disclosed may be made withoutdeparting from the spirit of the invention or the scope of the appendedclaims.

I claim:

1. In oil-filled electrical induction apparatus, in combination, aninsulating cylinder, a plurality of coaxial helical turns surroundingsaid cylinder wound from rectangular conductor strands disposed inside-by-side relation and having insulation permeable to the oil fillingsaid apparatus, a plurality of axially extending spacers between saidcylinder and said turns, a plurality of equally circumferentiallyseparated turn spacers attached respectively to said axial spacers andextending radially outward from said cylinder between said turns andpermitting access of said transformer oil to the permeable insulationcovering all of said conductor strands, said turns being held rigidlytogether as a unitary assembly and said conductor strands being bondedto said radial spacers by a fully cured and polymerized heat reactivecompound.

2. A winding for an oil-filled transformer comprising a plurality ofcoaxial, axially spaced, coil sections each comprising convolutions ofconductor of rectangular cross section in side-by-side relation andhaving solid insulation permeable to the oil filling said transformer,insulating members extending radially between said coil sections,certain of said insulating members being radial spacerscircumferentially spaced from each other permitting access oftransformer oil to the permeable insulation covering said convolutions,said coil sections being held rigidly together as a unitary assembly,and said convolutions being stayed by a polymeric heat reactive compoundbonding said conductor convolutions to said insulating members.

3. An electrical winding for an oil-filled transformer comprising aplurality of coaxial disk type coils each having a plurality ofconductor turns in side-by-side relationship and having solid insulationpermeable to the oil filling said transformer, annular insulatingwashers between certain of said coils, radial spacers circumferentiallyspaced from each other between certain others of said coils permittingaccess of oil to the permeable insulation covering all of said conductorturns, said coils being rigidly held together as a unitary assembly andsaid conductor turns being stayed in their relative positions by apolymeric heat reactive compound bonding said conductor turns to saidwashers and said radial spacers, said oil surrounding said winding andpenetrating said permeable insulation and replacing any air within saidinsulation.

4. An electrical winding in accordance with claim 3 wherein said coilsare arranged in pairs, said annular washers are between the coils ofeach pair, and said radial spacers are between said pairs.

5. An oil-filled electrical induction apparatus including a cylindricalinsulation barrier, a plurality of pairs of stacked disk coilssurrounding said barrier and radially spaced from said barrier to forman annular cylindrical passageway between said barrier and said stack ofcoils, each of said coils including conductor turns in side-by-siderelationship and having solid insulation permeable to the oil fillingsaid apparatus, a plurality of axial spacers extending in a directionparallel to the longitudinal axis of said barrier and circumferentiallyspaced from each other in said passageway, a plurality of relativelyrigid radial insulating spacers circumferentially spaced from eachbetween each of said pairs permitting access of oil to the permeableinsulation covering all of said conductor turns, said radial spacersbeing attached to said axial spacers, an annular insulating washerbetween the coils of each pair, said coils being rigidly held togetheras a unitary assembly and said turns being stayed and rigidly held intheir relative positions by a polymeric heat reactive compound bondingthe conductor turns to said radial spacers and to said annular washers.

6. The combination in an electrical winding for oilfilled inductionapparatus of a plurality of conductor turns of rectangular cross sectionhaving solid insulation permeable to the oil filling said apparatus,said conductor turns being in side-by-side relation and arranged inaxially spaced apart layers, the inside diameter of all of said layersbeing approximately equal and the outside diameter of all of said layersbeing approximately equal, insulating members extending between saidlayers certain of which are equiangularly spaced, radially extending,relatively rigid insulating spacers affording access of said oil to thepermeable insulation covering all of said conductor turns,

and retaining means for said spacers, said layers being rigidly heldtogether as a unitary assembly and said conductor turns being stayed intheir relative positions by a polymeric heat reactive compound bondingsaid conductor turns to said insulating members.

7. An oil-filled electrical apparatus including a cylindrical insulationbarrier, a plurality of conductor turns in side-by-side relationsurrounding said barrier and arranged in axially spaced apart layers,said turns being radially spaced from said barrier to form an annularcylindrical passageway therebetween and having insulation permeable tothe oil filling said apparatus, a plurality of axial spacers extendingin a direction parallel to the longitudinal axis of said barrier andcircumferentially spaced from each other in said passageway, insulatingmembers extending radially between said layers including a plurality ofradial spacers circumferentially spaced from each other between certainof said layers permitting access of oil to the permeable insulationcovering all of said turns, said radial spacers being attached to saidaxial spacers, said layers being held rigidly together as a unitaryassembly and said turns being stayed in their relative positions by apolymeric heat reactive compound bonding said turns to said insulatingmembers, said oil surrounding said layers and penetrating said permeableinsulation and replacing any air within said insulation.

8. An electrical induction apparatus including a magnetic core having aWinding leg, a first electric winding surrounding said winding leg, aplurality of coaxial insulating tubes surrounding said first winding, asecond electical winding surrounding said insulating tubes comprisingconductor turns of rectangular cross section in side-by-side relationand having solid insulation permeable to transformer oil and beingarranged in axially spaced apart layers, a plurality of insulating ringsdisposed at the ends of said second winding havingaxially extendingflanges fitting between said insulating tubes, said tubes and said ringsproviding an insulating barrier of high dielectric strength between saidfirst and second windings, a plurality of axially extending insulatingspacers between said barrier and said conductor turns, a plurality ofinsulating members extending radially between said rings and saidlayers, the insulating members between at least certain of said layerscomprising circumferentially spaced apart radial spacers attachedrespectively to said axial spacers and extending radially outward fromsaid barrier between said layers and affording transformer oil access tothe permeable insulation on all the conductor turns of said secondwinding, said layers and said end rings being rigidly held together andsaid conductor turns being rigidly stayed in their relative positions bya polymeric heat reactive compound bonding said conductor turns and saidrings to said insulating members.

9. In stationary induction apparatus, in combination, a magnetic corehaving a winding leg, a first electrical winding surrounding saidwinding leg, a plurality of concentric insulating tubes surrounding saidfirst winding, a second winding having a plurality of coaxial, spacedapart, coil sections each comprising a plurality of conductor turnssurrounding said tubes, said conductor turns having solid insulationpermeable to liquid dielectric, a plurality of insulating rings at theends of said second winding having axially extending flanges fittingbetween said insulating tubes, said tubes and said rings providing aninsulating barrier of high dielectric strength between said first andsecond windings, a plurality of axial spacing rods between said barrierand said coil sections, and a plurality of radially extending insulatingmembers between said coil sections and insulating rings, said rings andsaid coil sections being rigidly held together as a unitary assembly andsaid conductor turns being stayed against movement by a polymeric heatreactive compound bonding said turns and said rings to said insulatingmembers, the insulating members between certain of said coil sectionscomprising circumferentially separated radial spacers attached to saidaxial spacing rods and extending radially outward from said barrierbetween said coil sections and affording liquid dielectric access to thepermeable insulation covering all of the conductor turns of said secondwinding.

References Cited in the file of this patent UNITED STATES PATENTS1,938,421 Gilbert Dec. 5, 1933 2,571,418 Castenschiold Oct. 16, 1951FOREIGN PATENTS 335,557 Great Britain Sept. 24, 1930

